Regeneration and identification of interspecific asymmetric somatic hybrids obtained by donor-recipient fusion in cotton

Asymmetric hybrids between Gossypium hirsutum (YZ-1) and G. davidsonii were obtained by donor-recipient fusion. YZ-1 was considered the recipient and was pretreated with iodoacetamide (IOA), while G. davidsonii was considered the donor and was irradiated with ultraviolet (UV) before fusion. YZ-1 protoplasts stopped growth when treated with 0.5 mmol/L IOA for 20 min, and G. davidsonii protoplasts stopped growth when irradiated with 38.7 J/cm(2) UV for 30 s. Asymmetric somatic hybrids were obtained by electrofusion between the separately treated protoplasts of the 2 species. The regenerated plants were identified by morphological, cytological, and molecular analysis. Most regenerated plants derived from fused protoplasts displayed new morphology; some were intermediate between the two parents and a few displayed recipient-like morphology. Chromosome numbers in these somatic hybrids mostly ranged from 40 to 73. The hybridity was confirmed by random amplified polymorphic DNA and simple sequence repeat analysis. Organelle DNA inheritance of the YZ-1 and G. davidsonii somatic hybrid was investigated by cleaved amplified polymorphism sequence and chloroplast simple sequence repeat analysis, which indicated that recombination and rearrangements might have occurred in some regions of mitochondrial and chloroplastic DNA. This is the first report of completely asymmetric hybrid production via donor-recipient fusion between G. hirsutum and G. davidsonii, which is a novel case in hybrid production following the symmetric fusion and asymmetric fusion based on UV irradiation in cotton.